The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.
Not applicable.
The present invention relates to the manufacture of ink jet printhead and, in particular, discloses a method of manufacturing of a thermally actuated Ink Jet Printer.
Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet printheads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handling such precision devices often add a substantial expense in manufacturing.
Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits the amount of mass production throughput given any particular capital investment.
Additionally, more esoteric techniques are also often utilised. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S. Pat. No. 5,208,604), micro-punching, etc.
The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet printheads and therefore adds substantially to their final cost.
It would therefore be desirable if an efficient system for the mass production of ink jet printhead could be developed.
It is an object of the present invention to provide an alternative form of ink jet printing device suitable for use at high speeds and having a number of advantages over the prior art.
In accordance with a first aspect of the present invention, there is provided a method of manufacturing a thermally actuated ink jet printhead wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes. Preferably, multiple ink jet printheads are formed simultaneously on a single planar substrate such as a silicon wafer.
The printheads can be formed utilising standard vlsi/ulsi processing and can include integrated drive electronics formed on the same substrate. The drive electronics preferably being of a CMOS type. In the final construction, ink can be ejected from the substrate substantially normal to the substrate.
In accordance with a further aspect of the present invention, there is provided a method of manufacturing an ink jet printhead, the method comprising the steps of: (a) providing a semiconductor wafer having an electrical circuitry layer and a buried epitaxial layer formed thereon; (b) etching ink chamber cavities in the wafer, the etching stopping substantially at the epitaxial layer; (c) depositing and etching a first sacrificial material layer including vias for electrical interconnection of the electrical circuitry layer with subsequent layers; (d) depositing a first expansion layer of material having a high coefficient of thermal expansion over the ink chamber cavities; (e) depositing and etching a conductive material layer on the first expansion layer so as to form a heater element conductively interconnected to the electrical circuitry layer; (f) depositing and etching a second expansion layer of material having a high coefficient of thermal expansion over the conductive material layer, the etching including etching a shutter over each nozzle cavity; (g) back etching the wafer to the epitaxial layer; (h) etching a plurality of nozzle apertures, one for each ink chamber cavity, in the epitaxial layer; and (o) etching away the sacrificial layers.
The epitaxial layer can be utilized as an etch stop in step (b) which can comprise a plasma etch of the wafer.
The steps are preferably also utilized to simultaneously separate the wafer into separate printheads.